The invention relates to a process for the combinatorial preparation and testing of heterogeneous catalysts and catalysts obtained by this process.
To prepare and study novel chemical compounds, in addition to classical chemistry which is directed towards the synthesis and study of individual substances, combinatorial chemistry has developed. In this approach, a multiplicity of reactants were reacted in a one-pot synthesis and analysis was carried out as to whether the resultant reaction mixture displays the desired properties, for example a pharmacological activity. If an activity was found for such a reaction mixture, it was then necessary to determine in a further step which specific substance in the reaction mixture was responsible for the activity. In addition to the high expenditure for determining the actual active compound, it was difficult with a multiplicity of reactants to exclude to unwanted side reactions.
In another combinatorial synthesis approach, a multiplicity of compounds were synthesized by specific dosage and reaction of a number of reactants in a multiplicity of different reaction vessels. In this process, preferably, in each reaction vessel one reaction product is present, so that in the event of, for example, a given pharmacological activity of a mixture, the starting materials used for its preparation are known immediately.
In addition to the first applications of this more specific combinatorial synthesis in the search for novel pharmacologically active substances, very recently the synthesis method has also been extended to low-molecular-weight organic compounds and to organic and inorganic catalysts.
X.-D. Xiang et al., xe2x80x9cA Combinatorial Approach for Materials Discoveryxe2x80x9d, Science 268, (1995), pages 1738 to 1740 describe the preparation of BiSrCaCuO and YBaCuO superconductivity films on substrates, a combinatorial array of different metal compositions being obtained by physical masking processes and vapor deposition techniques in the deposition of the appropriate metals. After the calcination, different compositions are present at different positions of the array and can be studied by microprobes, for their conductivity for example.
WO 96/11878 describes, in addition to the preparation of such superconductivity arrays, the preparation of zeolites, the amounts required in each case being metered without prior mixing from a plurality of metal salt solutions using an ink jet onto a type of spot plate, a precipitation starting on addition of the last solution. BSCCO superconductors can also be prepared by separate metering of the individual nitrate solutions of the metals required by spraying onto a type of spot plate and subsequent heating.
Various types of heterogeneous catalysts can be prepared using the known processes. However, testing the catalysts is complex and frequently cannot be performed under realistic conditions, e.g. using the required residence times of the reactants on the catalyst, since the catalysts are present, for example, on a relatively large, generally flat support and this must be charged, for example, with a gas mixture to be reacted.
It is an object of the present invention to provide a process for preparing arrays of inorganic heterogeneous catalysts or their precursors in which the resultant catalysts can be tested with low expenditure and under conditions which resemble an industrial process. In addition, the disadvantages of the existing systems are to be avoided. Corresponding arrays are also to be provided.
Therefore, DE-A-198 05 719 proposed arrays of, preferably inorganic, heterogeneous catalysts and/or their precursors made up of a body which has, preferably parallel, through-channels in which at least n channels comprise n different, preferably inorganic, heterogeneous catalysts and/or their precursors, where n is 2, preferably 10, particularly preferably 100, in particular 1000, especially 10,000. The body can be a tube-bundle reactor or heat exchanger and the channels are tubes, or a block made of a solid material which has the channels, in the form of boreholes for example.
It is an object of the present invention to provide processes for preparing arrays of heterogeneous catalysts and/or their precursors which extend the spectrum of arrays accessible via WO.
We have found that this object is achieved by the processes described below for preparing arrays of heterogeneous catalysts and/or their precursors, made up of a body which has, preferably parallel, through-channels and in which at least n channels comprise n different heterogeneous catalysts and/or their precursors, where n is 2, preferably 10, particularly preferably 100, in particular 1,000, especially 10,000.
The term xe2x80x9carray of inorganic heterogeneous catalysts or their precursorsxe2x80x9d describes here an arrangement of different inorganic heterogeneous catalysts or their precursors on predetermined areas of a body which are spatially separate from one another, preferably a body having parallel through-channels, preferably a tube-bundle reactor or heat exchanger. The geometric arrangement of the individual areas to one another can be chosen freely in this case. For example, the areas can be arranged in the manner of a row (quasi one-dimensional) or a chessboard pattern (quasi two-dimensional). In a body having parallel through-channels, preferably a tube-bundle reactor or heat exchanger having a multiplicity of tubes parallel to one another, the arrangement becomes clear when a cross-sectional area perpendicular to the longitudinal axis of the tubes is considered: an area results, in which the individual tube cross sections reproduce the different areas separated from one another. The areas or tubes can, for example for tubes having a circular cross section, also be present in a dense packing, so that different rows are arranged from areas staggered to one another.
The term xe2x80x9cbodyxe2x80x9d describes a three-dimensional object which has a multiplicity (at least n) of through-channels. The channels thus connect two surface areas of the body and run through the body. Preferably, the channels are essentially, preferably completely, parallel to one another. In this case, the body can be made up of one or more materials and can be solid or hollow. It can have any suitable geometric shape. Preferably it has two surfaces parallel to one another in which in each case one orifice of the channels is situated. The channels preferably run perpendicularly to these surfaces. An example of a body of this type is a parallelepiped or cylinder in which the channels run between two parallel surfaces. However, a multiplicity of similar geometries is also conceivable.
The term xe2x80x9cchannelxe2x80x9d describes a connection running through the body between two orifices situated on the body surface which, for example, permits the passage of a fluid through the body. The channel here can have any desired geometry. It can have a cross-sectional area changing over the length of the channel or, preferably, can have a constant channel cross-sectional area. The channel cross section can have, for example, an oval, round or polygonal outlet with straight or rounded connections between the corners of the polygon. Preference is given to a round or equilateral polygonal cross section. Preferably, all channels in the body have the same geometry (cross section and length) and run parallel to one another.
The terms xe2x80x9ctube-bundle reactorxe2x80x9d and xe2x80x9cheat exchangerxe2x80x9d describe collective parallel arrangements of a multiplicity of channels in the form of tubes, where the tubes can have any desired cross section. The tubes are arranged in a fixed spatial relationship to one another, are preferably present spatially separated from one another and are preferably surrounded by a shell which encloses all of the tubes. By this means, for example, a heating or cooling medium can be conducted through the shell, so that all of the tubes can be heated or cooled uniformly.
The term xe2x80x9cblock of a solid materialxe2x80x9d describes a body of a solid material (which in turn can be made up of one or more starting materials) which has the channels, for example in the form of boreholes. The geometry of the channels (boreholes) can here be chosen freely as described above for the channels generally. The channels (boreholes) need not be installed by boring, but can be left open, for example even when forming the solid body/block, for instance by extruding an organic and/or inorganic molding composition (for example by an appropriate die geometry during extrusion). In contrast to the tube-bundle reactors or heat exchangers, the space in the body between the channels in the block is always filled by the solid material. Preferably, the block is made up of one or more metals.
The term xe2x80x9cpredeterminedxe2x80x9d means that, for example, a number of different catalysts or catalyst precursors is introduced into a tube-bundle reactor or heat exchanger in such a manner that the assignation of the different catalysts or catalyst precursors to the individual tubes is recorded and can later be retrieved, for example, when determining the activity, selectivity and/or long-term stability of the individual catalyst in order to make possible an unambiguous assignation of defined measured values to defined catalyst compositions. Preferably, the catalysts or their precursors are prepared and distributed to the different tubes of the tube-bundle reactor under computer control, the respective composition of a catalyst and the position of the tube in the tube-bundle reactor into which the catalyst or catalyst precursor is introduced is stored in the computer and can later be retrieved. The term xe2x80x9cpredeterminedxe2x80x9d thus serves to differentiate from a chance or random distribution of the generally different catalysts or catalyst precursors to the tubes of a tube-bundle reactor.
The arrays according to the invention of preferably inorganic, heterogeneous catalysts and/or their precursors can be prepared according to the invention by a variety of processes:
Process a comprises the following steps:
a1) preparing solutions, emulsions and/or dispersions of elements and/or element compounds of the chemical elements present in the catalyst and/or catalyst precursor and, if appropriate preparing dispersions of inorganic support materials,
a2) if appropriate introducing adhesion promoters, binders, viscosity regulators, pH regulators and/or solid inorganic supports into the solutions, emulsions and/or dispersions,
a3) simultaneously or successively coating the channels of the body with the solutions, emulsions and/or dispersions, a predetermined amount of the solutions, emulsions and/or dispersions being introduced into each channel to obtain a predetermined composition, to produce freshly impregnated moist channels.
a4) treating and reacting with one or more reactive gases the freshly impregnated moist channels obtained after the coating, and
a5) if appropriate heating the coated body in the presence or absence of inert gases or reactive gases to a temperature in the range from 20 to 1500xc2x0 C. to dry, with or without sintering or calcining, the catalysts and/or catalyst precursors.
The process b comprises the following steps:
b1) preparing solutions, emulsions and/or dispersions of elements and/or element compounds of the elements present in the catalyst and/or catalyst precursor and, if appropriate preparing dispersions of inorganic support materials,
b2) if appropriate introducing adhesion promoters, binders, viscosity regulators, pH regulators and/or solid inorganic supports into the solutions, emulsions and/or dispersions,
b3) simultaneously or successively coating catalyst supports present in the channels of the body with the solutions, emulsions and/or dispersions, a predetermined amount of the solutions, emulsions and/or dispersions being introduced into each channel to obtain a predetermined composition on the catalyst supports,
b4) treating and reacting with one or more reactive gases the freshly impregnated moist channels obtained after the coating, and
b5) if appropriate heating the body comprising the coated catalyst supports in the channels in the presence or absence of inert gases or reactive gases to a temperature in the range from 20 to 1500xc2x0 C. to dry, with or without sintering or calcining, the catalysts and/or catalyst precursors.
Process c) comprises the following steps:
c1) preparing solutions, emulsions and/or dispersions of elements and/or element compounds of the chemical elements present in the catalyst and/or catalyst precursor and, if appropriate preparing dispersions of inorganic support materials,
c2) mixing predetermined amounts of the solutions, emulsions and/or dispersions with or without precipitation aids in one or more reaction vessels run in parallel,
c3) if appropriate introducing adhesion promoters, binders, viscosity regulators, pH regulators and/or solid inorganic supports into the resultant mixture(s),
c4) coating one or more predetermined channels of the body with the mixture or a plurality of mixtures,
c5) repeating steps c2) to c4) for other channels of the body until the channels containing the respective predetermined catalyst and/or catalyst precursor compositions are coated,
c6) treating and reacting with one or more reactive gases the freshly impregnated moist channels obtained after the coating, and
c7) if appropriate heating the coated body in the presence or absence of inert gases or reactive gases to a temperature in the range from 20 to 1500xc2x0 C. to dry, with or without sintering or calcining, the catalysts and/or catalyst precursors.
Preferably, it comprises the following steps,
c1) preparing solutions of element compounds of the chemical elements present in the catalyst except for oxygen, and if appropriate preparing dispersions of inorganic support materials
c2) mixing predetermined amounts of the solutions or dispersions with or without precipitation aids in one or more reaction vessels run in parallel with precipitation of the chemical elements present in the catalyst,
c3) if appropriate introducing adhesion promoters, binders, viscosity regulators, pH regulators and/or solid inorganic supports into the resultant suspension,
c4) coating with the suspension one or more predetermined tubes of the tube-bundle reactor or heat exchanger,
c5) repeating steps c2) to c4) for different tubes of the tube-bundle reactor or heat exchanger until the tubes containing the respective predetermined catalyst compositions are coated,
c6) treating and reacting with one or more reactive gases the freshly impregnated moist channels obtained after the coating, and
c7) heating the coated tube-bundle reactor or heat exchanger in the presence or absence of inert gases or reactive gases to a temperature in the range from 20 to 1500xc2x0 C. to dry, with or without sintering or calcining, the catalysts.
Process d) comprises the following steps:
d1) preparing solutions, emulsions and/or dispersions of elements and/or element compounds of the chemical elements present in the catalyst and/or catalyst precursor and, if appropriate preparing dispersions of inorganic support materials,
d2) mixing predetermined amounts of the solutions, emulsions and/or dispersions with or without precipitation aids in one or more reaction vessels run in parallel,
d3) if appropriate introducing adhesion promoters, binders, viscosity regulators, pH regulators and/or solid inorganic supports into the resultant mixture(s),
d4) coating catalyst supports present in one or more predetermined channels of the body with the mixture or one or more of the mixtures,
d5) repeating steps d2) to d4) for other (that is generally the as yet uncoated) catalyst supports in the channels of the body until (preferably all) the catalyst supports present in the channels of the body are coated with the respective predetermined (generally differing from one another) catalyst compositions and/or catalyst precursor compositions,
d6) treating and reacting with one or more reactive gases the freshly impregnated moist channels obtained after the coating, and
d7) if appropriate heating the body comprising the coated catalyst supports in the channels in the presence or absence of inert gases or reactive gases to a temperature in the range from 20 to 1500xc2x0 C. to dry, with or without sintering or calcining, the catalysts and/or catalyst precursors.
In this process, the adhesiveness of the channels (e.g. of the inner surface of the tubes) of the body or of the catalyst supports can be increased prior to the coating by chemical, physical or mechanical pretreatment of the inner walls of the channels (e.g. inner tubes) or the catalyst supports or by applying an adhesive layer. This applies in particular to the processes a) and c) and to b) and d) respectively.
Process e comprises the following steps:
e1) reacting predetermined dry porous catalyst supports with one or more reactive gases for preparing predetermined supported catalysts outside or inside the body,
e2) if appropriate introducing the supported catalysts prepared outside the body into predetermined channels of the body, and
e3) if appropriate heating the filled body in the presence or absence of inert gases or reactive gases to a temperature in the range from 20 to 1500xc2x0 C. to dry, with or without sintering or calcining, the catalysts.
Process f) comprises the following steps:
f1) coating and if appropriate heating predetermined catalyst supports to prepare predetermined supported catalysts in the manner defined above in processes b) and d) outside the body,
f2) introducing the supported catalysts into predetermined chapels of the body,
f3) if appropriate heating the packed body in the presence or absence of inert gases or reactive gases to a temperature in the range from 20 to 1500xc2x0 C. to dry, with or without sintering or calcining, the catalysts.
Preferably, the external shape of the supported catalysts corresponds here to the shape of the channel interior in the body at least essentially, preferably approximately or completely.
Process g) comprises the following steps:
g1) simultaneous or sequential coating of the channels of the body with gasified chemical elements or their mixtures of the chemical elements present in the catalyst, and
g2) if appropriate heating the coated body in the presence or absence of inert gases or reactive gases to a temperature in the range of from 20 to 1500xc2x0 C. to dry, with or without sintering or calcining, the catalysts and/or catalyst precursors.
Process h) comprises the following steps:
h1) simultaneous or sequential coating of the channels of the body with pulverulent chemical elements or their mixtures of the chemical elements present in the catalyst, and
h2) if appropriate heating the coated body in the presence or absence of inert gases or reactive gases to a temperature in the range of from 20 to 1500xc2x0 C. to dry, and if appropriate sinter or calcine, the catalysts and/or catalyst precursors.
The invention also relates to inorganic heterogeneous catalyst arrays which are obtainable by one of the abovementioned processes. The arrays can also be prepared by any combination of the abovementioned processes.
The processes are suitable for preparing a multiplicity of catalyst systems, as are described, for example, in G. Ertl, H. Knxc3x6zinger, J. Weitkamp, editors, xe2x80x9cHandbook of Heterogeneous Catalysisxe2x80x9d, Wiley-VCH, Weinheim, 1997.
In addition, the invention relates to a process i) for determining catalytic properties, in particular the activity, selectivity and/or long-term stability of the catalysts described above and below in an array described, which comprises the following steps:
i1) if appropriate activating the catalysts in the body,
i2) heating or cooling the body to a desired reaction temperature,
i3) passing a fluid reactant or a fluid reaction mixture through (one, a plurality or all of the) channels of the body,
i4) (preferably separate) discharge of the reacted fluids from individual or a plurality of collective channels of the body,
i5) (preferably separate) analysis of the discharged reacted fluids,
i6) if appropriate comparative evaluation of the analytical results of a plurality of analyses.
In a preferred process variant, after heating or cooling the body to a first reaction temperature in step i2), steps i3) to, i6) are carried out successively for a plurality of different fluid reactants or fluid reaction mixtures, where in each case a purge step with a purge gas can be introduced, and then the body can be heated or cooled to a second reaction temperature and the abovementioned reactions can be repeated at this temperature.
At the start of the analysis, the collected gas stream of the entire array can be analyzed to detect whether there has been any reaction at all. Thereafter, if a reaction is present, the discharges of the individual tubes or a plurality of tubes can be analyzed to determine an optimum catalyst using a minimum number of analytical processes.
Flow can pass rough individual tubes or a plurality or all of the tubes collectively.
Preferably, the fluid reactant or fluid reaction mixture is a gas or gas mixture.
The invention permits the automated preparation and catalytic testing for the purpose of mass screening of heterogeneous catalysts for chemical reactions, in particular for reactions in the gas phase, very particularly for partial oxidations of hydrocarbons in the gas phase by molecular oxygen (gas-phase oxidations).
Suitable reactions for investigation are described in G. Ertl, H. Knxc3x6zinger, J. Weitkamp, editors, xe2x80x9cHandbook of Heterogeneous Catalysisxe2x80x9d, Wiley-VCH, Weinheim 1997. Examples of suitable reactions are principally listed in this reference in Volumes 4 and 5 under numbers 1, 2, 3 and 4.
Examples of suitable reactions are the decomposition of nitrogen oxides, the synthesis of ammonia, the oxidation of ammonia, oxidation of hydrogen sulfide to sulfur, oxidation of sulfur dioxide, direct synthesis of methylchlorosilanes, oil refining, oxidative coupling of methane, methanol synthesis, hydrogenation of carbon monoxide and carbon dioxide, conversion of methanol to hydrocarbons, catalytic reforming, catalytic cracking and hydrocracking, coal gasification and liquefaction, fuel cells, heterogeneous photocatalysis, synthesis of MTBE and TAME, isomerizations, alkylations, aromatizations, dehydrogenations, hydrogenations, hydroformylations, selective or partial oxidations, aminations, halogenations, nucleophilic aromatic to substitutions, addition and elimination reactions, oligomerizations and metathesis, polymerizations, enantioselective catalysis and biocatalytic reactions.